can someone clue me in, im new to the concept of buying a controller keyboard and using it with my computer.
what are sound fonts? how do i use them? and where can i get them?
and what do you think of soundfonts, useless or invaluable?

Soundfonts are files that contain samples of various instruments (eg. a piano soundfont etc.) Load it up to a sampler and you'll be able to play the sound. Not widely used nowdays though but most software samplers and sequencers can easily import them.

They are just collections of multisamples collected into a big file. You need a software sampler like Native Instruments Kontakt or similar to use the sounds inside them. Multisamples mean that each sound is sampled from many parts of the keyboard on the original synth, and they are laid out across the sampler's keyboard so that when you play in octave C0-C1, it will play sample1.wav, from C1-C2, it plays sample2.wav etc.

This is because samples need to stretch in time as you move away from the original sampled tone. One octave higher means twice the frequency, and it will play the sample twice as fast. To defeat this, they multisample from many places on the keyboard.
They are certainly not useless, since they are REAL samples of the real synths, and if the quality is good it will sound exactly like the real synth when you play it.

Then you have the thousands of VSTi synths, that don't use samples but generate the sound internally, like a Virtual analog synth would.
There are lots of emulations of real analog classics like the Minimoog, Moog Modular system, Prophet-5 or CS-80 made by Arturia, native instruments, wayoutware (a perfect ARP2600 remake) and lots more. You just open them and play with your MIDI keyboard that is connected to your computer. If your soundcard doesn't have its own MIDI interface, you will need that too, or you cannot connect the keyboard to your computer at all.

thanks for the info.
sounds cool to get a software sampler that supports soundfonts for things like pianos,strings,bells and workstation type stuff.
can NI kontakt do any synth noises or is it strictly a sampler? and are the soundfonts free if i buy NI kontakt?
im asking becuase im new to software so ill most likly just be using one program for a while, like a software synth, or something that supports soundfonts.

Most soundfonts are free, just google "soundfonts" and a ton of websites will show up. Kontakt is pretty complicated if you're only starting, but it's strictly a sampler. Programs like FL Studio and Reason can handle soundfonts, as well as having built in synths.